Leymus chinensis （Trin.） Tzveh is a rhizomatous perennial herbage of Gramineae. Reproduction is mainly by vegetative reproduction. Tillering nodes and rhizomes of L. chinensis serve as organs for both vegetative reproduction and nutrient storage. Water-soluble carbohydrate （WSC） contents were measured in tillering nodes, nodes and Internodes of rhizomes of different age classes of L. chinensis populations at three development stages, namely the dough ripe stage, the vegetative growth stage after full ripeness, and the withering stage, in two habitats： sandy soil and saline-alkaline soil. The results showed that WSC content in tillering nodes of the three age classes of L. chinensis were all markedly decreased with increasing age in both sandy soil and saline-alkaline solh A similar trend of changes In WSC contents was observed in the nodes and internodes of rhizomes in different age classes In both habitats. The highest WSC contents were in 2-age-class nodes and internodes of rhizomes, followed by those In the 1 age class, with the lowest WSC contents found in 3-age-class nodes and internodes of rhizomes at the dough ripe and vegetative growth stages after full ripening. In turn, WSC contents decreased with Increasing age at the withering stage in both habitats. The WSC content in each age class of internode was higher than that in the node of rhizome at three development stages in both habitats.
Through a gradient experiment controlling CO2 concentration and illumination intensity, the photosynthetic physiological characters of two C4 pathway plants, Setaria viridis and Pennisetum flaccidum, were measured on the Songnen Plains of China. The results showed that the net photosynthetic rate (Pn) of S.viridis was higher than P.flaccidum. As the CO2 concentration increased, Pn of the two species both increased until the CO2 concentration reached approximately 600 μmol/mol, after which Pn decreased. At the same time, the light compensation points of the two species gradually dropped. This is related to the inhibition of dark respiration with high CO2 concentration.
